#include "aes_impl.h"
#include <string.h>

/* AES S-boxAnd逆S-box表 */
static const uint8_t sbox[256] = {
    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
};

static const uint8_t inv_sbox[256] = {
    0x52,0x09,0x6a,0xd5,0x30,0x36,0xa5,0x38,0xbf,0x40,0xa3,0x9e,0x81,0xf3,0xd7,0xfb,
    0x7c,0xe3,0x39,0x82,0x9b,0x2f,0xff,0x87,0x34,0x8e,0x43,0x44,0xc4,0xde,0xe9,0xcb,
    0x54,0x7b,0x94,0x32,0xa6,0xc2,0x23,0x3d,0xee,0x4c,0x95,0x0b,0x42,0xfa,0xc3,0x4e,
    0x08,0x2e,0xa1,0x66,0x28,0xd9,0x24,0xb2,0x76,0x5b,0xa2,0x49,0x6d,0x8b,0xd1,0x25,
    0x72,0xf8,0xf6,0x64,0x86,0x68,0x98,0x16,0xd4,0xa4,0x5c,0xcc,0x5d,0x65,0xb6,0x92,
    0x6c,0x70,0x48,0x50,0xfd,0xed,0xb9,0xda,0x5e,0x15,0x46,0x57,0xa7,0x8d,0x9d,0x84,
    0x90,0xd8,0xab,0x00,0x8c,0xbc,0xd3,0x0a,0xf7,0xe4,0x58,0x05,0xb8,0xb3,0x45,0x06,
    0xd0,0x2c,0x1e,0x8f,0xca,0x3f,0x0f,0x02,0xc1,0xaf,0xbd,0x03,0x01,0x13,0x8a,0x6b,
    0x3a,0x91,0x11,0x41,0x4f,0x67,0xdc,0xea,0x97,0xf2,0xcf,0xce,0xf0,0xb4,0xe6,0x73,
    0x96,0xac,0x74,0x22,0xe7,0xad,0x35,0x85,0xe2,0xf9,0x37,0xe8,0x1c,0x75,0xdf,0x6e,
    0x47,0xf1,0x1a,0x71,0x1d,0x29,0xc5,0x89,0x6f,0xb7,0x62,0x0e,0xaa,0x18,0xbe,0x1b,
    0xfc,0x56,0x3e,0x4b,0xc6,0xd2,0x79,0x20,0x9a,0xdb,0xc0,0xfe,0x78,0xcd,0x5a,0xf4,
    0x1f,0xdd,0xa8,0x33,0x88,0x07,0xc7,0x31,0xb1,0x12,0x10,0x59,0x27,0x80,0xec,0x5f,
    0x60,0x51,0x7f,0xa9,0x19,0xb5,0x4a,0x0d,0x2d,0xe5,0x7a,0x9f,0x93,0xc9,0x9c,0xef,
    0xa0,0xe0,0x3b,0x4d,0xae,0x2a,0xf5,0xb0,0xc8,0xeb,0xbb,0x3c,0x83,0x53,0x99,0x61,
    0x17,0x2b,0x04,0x7e,0xba,0x77,0xd6,0x26,0xe1,0x69,0x14,0x63,0x55,0x21,0x0c,0x7d
};

static const uint8_t Rcon[11] = {0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36};

/* GF(2^8)乘法 */
#define xtime(x) ((x<<1) ^ (((x>>7) & 1) * 0x1b))
#define Multiply(x,y) (((y & 1) * x) ^ ((y>>1 & 1) * xtime(x)) ^ ((y>>2 & 1) * xtime(xtime(x))) ^ \
                       ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))

/* Key扩展 */
static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key) {
    uint32_t i, j, k;
    uint8_t tempa[4];
    
    for (i = 0; i < 4; ++i) {
        RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
        RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
        RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
        RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
    }
    
    for (i = 4; i < 44; ++i) {
        k = (i - 1) * 4;
        tempa[0] = RoundKey[k + 0];
        tempa[1] = RoundKey[k + 1];
        tempa[2] = RoundKey[k + 2];
        tempa[3] = RoundKey[k + 3];
        
        if (i % 4 == 0) {
            const uint8_t u8tmp = tempa[0];
            tempa[0] = tempa[1];
            tempa[1] = tempa[2];
            tempa[2] = tempa[3];
            tempa[3] = u8tmp;
            
            tempa[0] = sbox[tempa[0]];
            tempa[1] = sbox[tempa[1]];
            tempa[2] = sbox[tempa[2]];
            tempa[3] = sbox[tempa[3]];
            
            tempa[0] = tempa[0] ^ Rcon[i/4];
        }
        
        j = i * 4; k = (i - 4) * 4;
        RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
        RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
        RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
        RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
    }
}

static void AddRoundKey(uint8_t round, uint8_t* state, const uint8_t* RoundKey) {
    uint8_t i,j;
    for (i = 0; i < 4; ++i) {
        for (j = 0; j < 4; ++j) {
            state[i*4+j] ^= RoundKey[(round * 16) + (i * 4 + j)];
        }
    }
}

static void SubBytes(uint8_t* state) {
    uint8_t i;
    for (i = 0; i < 16; ++i) {
        state[i] = sbox[state[i]];
    }
}

static void ShiftRows(uint8_t* state) {
    uint8_t temp;
    temp = state[1]; state[1] = state[5]; state[5] = state[9]; state[9] = state[13]; state[13] = temp;
    temp = state[2]; state[2] = state[10]; state[10] = temp;
    temp = state[6]; state[6] = state[14]; state[14] = temp;
    temp = state[3]; state[3] = state[15]; state[15] = state[11]; state[11] = state[7]; state[7] = temp;
}

static void MixColumns(uint8_t* state) {
    uint8_t i, Tmp, Tm, t;
    for (i = 0; i < 4; ++i) {
        t   = state[i*4];
        Tmp = state[i*4] ^ state[i*4+1] ^ state[i*4+2] ^ state[i*4+3];
        Tm  = state[i*4] ^ state[i*4+1]; Tm = xtime(Tm); state[i*4] ^= Tm ^ Tmp;
        Tm  = state[i*4+1] ^ state[i*4+2]; Tm = xtime(Tm); state[i*4+1] ^= Tm ^ Tmp;
        Tm  = state[i*4+2] ^ state[i*4+3]; Tm = xtime(Tm); state[i*4+2] ^= Tm ^ Tmp;
        Tm  = state[i*4+3] ^ t; Tm = xtime(Tm); state[i*4+3] ^= Tm ^ Tmp;
    }
}

static void InvSubBytes(uint8_t* state) {
    uint8_t i;
    for (i = 0; i < 16; ++i) {
        state[i] = inv_sbox[state[i]];
    }
}

static void InvShiftRows(uint8_t* state) {
    uint8_t temp;
    temp = state[13]; state[13] = state[9]; state[9] = state[5]; state[5] = state[1]; state[1] = temp;
    temp = state[2]; state[2] = state[10]; state[10] = temp;
    temp = state[6]; state[6] = state[14]; state[14] = temp;
    temp = state[7]; state[7] = state[11]; state[11] = state[15]; state[15] = state[3]; state[3] = temp;
}

static void InvMixColumns(uint8_t* state) {
    int i;
    uint8_t a, b, c, d;
    for (i = 0; i < 4; ++i) {
        a = state[i*4]; b = state[i*4+1]; c = state[i*4+2]; d = state[i*4+3];
        state[i*4]   = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
        state[i*4+1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
        state[i*4+2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
        state[i*4+3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
    }
}

void AES_Impl_Init(AES_Impl_Context* ctx, const uint8_t* key, const uint8_t* iv) {
    KeyExpansion(ctx->round_key, key);
    if (iv != NULL) {
        memcpy(ctx->iv, iv, AES_IMPL_BLOCK_SIZE);
    } else {
        memset(ctx->iv, 0, AES_IMPL_BLOCK_SIZE);
    }
}

void AES_Impl_Encrypt_Block(const AES_Impl_Context* ctx, const uint8_t* input, uint8_t* output) {
    uint8_t state[16];
    uint8_t round = 0;
    
    memcpy(state, input, 16);
    AddRoundKey(0, state, ctx->round_key);
    
    for (round = 1; round < 10; ++round) {
        SubBytes(state);
        ShiftRows(state);
        MixColumns(state);
        AddRoundKey(round, state, ctx->round_key);
    }
    
    SubBytes(state);
    ShiftRows(state);
    AddRoundKey(10, state, ctx->round_key);
    
    memcpy(output, state, 16);
}

void AES_Impl_Decrypt_Block(const AES_Impl_Context* ctx, const uint8_t* input, uint8_t* output) {
    uint8_t state[16];
    uint8_t round = 0;
    
    memcpy(state, input, 16);
    AddRoundKey(10, state, ctx->round_key);
    
    for (round = 9; round > 0; --round) {
        InvShiftRows(state);
        InvSubBytes(state);
        AddRoundKey(round, state, ctx->round_key);
        InvMixColumns(state);
    }
    
    InvShiftRows(state);
    InvSubBytes(state);
    AddRoundKey(0, state, ctx->round_key);
    
    memcpy(output, state, 16);
}

void AES_Impl_CBC_Encrypt(AES_Impl_Context* ctx, const uint8_t* input, uint8_t* output, uint32_t length) {
    uint32_t i;
    uint8_t block[16];
    
    for (i = 0; i < length; i += 16) {
        for (uint8_t j = 0; j < 16; ++j) {
            block[j] = input[i + j] ^ ctx->iv[j];
        }
        AES_Impl_Encrypt_Block(ctx, block, output + i);
        memcpy(ctx->iv, output + i, 16);
    }
}

void AES_Impl_CBC_Decrypt(AES_Impl_Context* ctx, const uint8_t* input, uint8_t* output, uint32_t length) {
    uint32_t i;
    uint8_t next_iv[16], block[16];
    
    for (i = 0; i < length; i += 16) {
        memcpy(next_iv, input + i, 16);
        AES_Impl_Decrypt_Block(ctx, input + i, block);
        for (uint8_t j = 0; j < 16; ++j) {
            output[i + j] = block[j] ^ ctx->iv[j];
        }
        memcpy(ctx->iv, next_iv, 16);
    }
}
